UPDATING CONTACT INFORMATION FOR CLIENT DEVICES REGISTERED TO THE SAME USER FOR AN INTERNET PROTOCOL MULTIMEDIA SUBSYSTEM SERVICE

In an embodiment, a single registrar component of an Internet Protocol (IP) Multimedia Subsystem (IMS) network, receives a request to register a client device associated with a user to an IMS service. The single registrar component sends an acknowledgment to the request that indicates an assignment of device-specific routing identifier(s) (e.g., GRUUs) for the client device. The acknowledgment is further configured to include an indication other device-specific routing identifier(s) for other client device(s) that have already registered to the IMS service in association with the same user.